With the new year comes new goals, and these goals often include getting into better physical shape. For many, this means incorporating new and different food and drinks, such as protein-rich shakes centered on Greek yogurt or protein powders.

But choosing the right protein powder can be challenging. Rachel Welp, group leader of Mackie Shilstone's seven GNC franchise locations, says that protein powders are among the most commonly asked questions she hears. "It can be confusing for people; they want to be sure that they're choosing the protein powder that's best for them," she said.

So let's start by saying that no one needs to incorporate protein powder in order to have a healthy diet or to reach their fitness goals.

But protein powders are a convenient way to boost protein intake, and can easily be incorporated into shakes and baked goods like muffins and brownies, as well as pancakes and homemade granola. Protein powder also can be dissolved into milk or almond milk and stirred into oatmeal or poured over breakfast cereal.

When deciding what type of protein powder to use, one of the most important factors is that you actually like the way it tastes. If it's just not palatable to you, it's not likely that you'll stick with it.

Many brands are available in single-serve packets, making it easy to taste-test before investing in a full-size container. And some stores, like Whole Foods, allow customers to return protein powder that has been opened for a store credit or exchange, or a refund with receipt. GNC will take back opened protein powders within 30 days (with receipt) for store credit, exchange, or refund, and Vitamin Shoppe will give a store credit or exchange, no receipt needed.

Once the issue of taste is out of the way, there's the question of what type of protein powder is best for you. Websites and shelves are filled with an ever-increasing number of types of protein, from whey to egg to plant-based options like hemp, soy, and pea protein. Then there's the option of a protein concentrate or protein isolate – it can be more than overwhelming.

Simply put, protein isolates are a purer source of the protein, containing at least 90 percent protein, while protein concentrates contain less protein, and more carbs and fat.

There's also a lot of variation in how well the different types of protein powders are digested and assimilated by the body. There's a value referred to as the Protein Digestibility Corrected Amino Acid Score (PDCAAS) that ranks protein quality on a scale of zero to one.

Here's a summary of the various types of protein powders, including the PDCAAS for each.

Whey protein (PDCAAS – 1.00). Whey protein makes up 20 percent of the protein in milk. It is in the clear liquid part of milk that is strained off when making cheese or cottage cheese. Whey protein concentrates contain just 70 to 90 percent protein and whey protein isolates contain at least 90 percent protein. Whey protein hydrolysate, processed to break down the longer protein chains into smaller fragments, is an even purer form of whey protein. This type of whey protein is essentially 'pre-digested' so that it's the easiest for the body to utilize, making it a great protein to use pre- and post-workout. Whey protein hydrolysate can be cost-prohibitive, but whey protein isolate is still an excellent option for those looking for a more budget-friendly alternative.

Whey isolate and whey hydrolysate are both low in lactose, and can often be tolerated even by those with lactose intolerance.

Casein protein (PDCAAS – 1.00). Casein accounts for the other 80 percent of the protein in milk. It is a slow-digesting protein, resulting in a slow release of amino acids. I typically recommend casein before bedtime to minimize muscle losses through the night, though Welp points out that casein can be useful anytime throughout the day for those looking for a protein source that will keep them fuller, longer.

Egg white protein (PDCAAS – 1.00). Egg white protein is a medium-digested protein that can be a good fit for those who can't consume soy or dairy, although the feedback that I get from most clients is that they don't like the taste of egg protein as much as whey or soy.

Soy protein (PDCAAS – 1.00). Soy is a complete protein, meaning that it contains all of the essential amino acids, just as whey and egg protein do. It is slowly digested and absorbed, Welp said, so it's not the best choice for post-workout recovery. It can be beneficial in managing cholesterol and blood sugar, however -- supplementing with 25 to 30 grams of soy protein daily has been shown to help reduce LDL cholesterol levels and can help to stabilize blood sugar levels.

Soy protein is high in isoflavones, compounds that have estrogen-like effects on the body, so Welp recommends that men -- particularly older men who might have low testosterone levels -- not consume more than 25 grams of soy protein a day.

Other plant-based proteins: Hemp protein (PDCAAS – 0.46), rice protein (PDCAAS – 0.47), and pea protein (PDCAAS – 0.69). For years, soy protein was the main vegetarian or vegan option for protein powder on most store shelves. Now, however, we're seeing a wider array of products centered on plant-based proteins like hemp, rice and pea protein. These protein powders can be beneficial for people with milk or soy allergies, as well as those looking for vegan options. They're typically higher in carbs with a lower protein content (hemp protein powder is often just 50 percent protein), so more protein powder needs to be consumed in order to get the same amount of protein.